Devices, systems and methods for purging and loading sorbent tubes

ABSTRACT

Certain embodiments described herein are directed to devices that can be used in purging and loading applications. In some examples, a device configured to purge a sorbent tube until a desired water level is reached is provided. In other examples, a device configured to load a sorbent tube with a desired water level is provided. Systems and methods using the devices are also described.

TECHNOLOGICAL FIELD

Certain features, aspects and embodiments are directed to devices thatcan be used in purging and loading applications. In particular, certainembodiments described herein are directed to devices, systems andmethods that can be used to reduce water within a sorbent tube to adesired level prior to sampling.

SUMMARY

In a first aspect, a device comprising a humidity sensor constructed andarranged to fluidically couple to a sorbent tube, the humidity sensorconfigured to receive a fluid stream from the sorbent tube to determinethe level of water in the sorbent tube is provided.

In certain embodiments, the humidity sensor can be configured to detectan inflection point as an indicator of a desired level of water in thesorbent tube. In some embodiments, the device comprising the humiditysensor can be configured to receive the sorbent tube. In otherembodiments, the device comprising the humidity sensor can be configuredto fluidically couple to a separate receptacle comprising the sorbenttube. In some examples, the device can include a plurality ofreceptacles each configured to receive a single sorbent tube. In otherexamples, the device can include a plurality of humidity sensors inwhich each of the plurality of receptacles can be fluidically coupled toone of the plurality of humidity sensors. In certain examples, thedevice can include a temperature sensor. In some embodiments, the devicecan include a switching valve fluidically coupled to the device. Inadditional embodiments, the device can include a purging gas sourcecoupled to the switching valve.

In other embodiments, the device can include a humidity sensorelectrically coupled to a processor. In some examples, the processor canbe configured to stop flow of purging gas from the purging gas source tothe sorbent tube when the humidity sensor detects a water level in thereceived fluid stream below a selected water level. In other examples,the selected water level can be 3% relative humidity or less. In someembodiments, the switching valve can be actuated by the processor tostop flow of the purging gas to the sorbent tube when the humiditysensor detects a water level in the received fluid stream below aselected water level. In certain embodiments, fluid flow from thepurging gas source can be stopped by the processor to stop flow of thepurging gas to the sorbent tube when the humidity sensor detects a waterlevel in the received fluid stream below a selected water level. Inother examples, the device can include a temperature sensor and aprocessor, in which the processor is electrically coupled to thehumidity sensor and to the temperature sensor, the processor configuredto calculate the water level in the fluid stream received by thehumidity sensor using a humidity signal from the humidity sensor and atemperature signal from the temperature sensor.

In another aspect, a device comprising an inlet fluidically coupled to aplurality of receptacles each configured to receive at least one sorbenttube, the device further comprising an outlet fluidically coupled to atleast one humidity sensor configured to receive a fluid stream from atleast one of the plurality of receptacles to determine the level ofwater in a sorbent tube in the receptacle providing the fluid stream tothe humidity sensor is described.

In certain examples, the device can include at least one temperaturesensor coupled to the device. In other examples, the device can includean inlet and an outlet for each of the plurality of receptacles. In someembodiments, the device can include a switching valve fluidicallycoupled to the outlets of the receptacles. In further embodiments, theswitching valve can be configured to provide fluidic coupling between asingle receptacle and the humidity sensor. In additional embodiments,the switching valve is configured to provide fluidic coupling betweentwo receptacles and the humidity sensor. In some examples, the devicecomprises a switching valve in each of the outlets of the plurality ofreceptacles. In further examples, the device can include a switchingvalve in each of the inlets of the plurality of receptacles. In certainembodiments, the device comprises a plurality of humidity sensors eachfluidically coupled to a single receptacle of the plurality ofreceptacles. In other embodiments, each of the plurality of humiditysensors can be electrically coupled to a processor. In some embodiments,at least one of the plurality of receptacles can be configured toreceive two sorbent tubes. In further embodiments, at least tworeceptacles of the plurality of receptacles have different dimensions.In some examples, at least one receptacle comprises an inlet sizesmaller than an inlet size of another receptacle in the plurality ofreceptacles. In certain examples, the device further comprises an inletand an outlet for each of the plurality of receptacles, at least onehumidity sensor fluidically coupled to each of the plurality ofreceptacles, and at least one temperature sensor in at least one outletof the plurality of receptacles. In some examples, the device caninclude a plurality of humidity sensors each fluidically coupled to asingle receptacle of the plurality of receptacles.

In an additional aspect, a sorbent tube comprising a body for receivinga sorbent material, the body comprising a first end and a second endopposite the first end, the second end of the body configured to receivea humidity sensor configured to detect water in the sorbent tube isdisclosed.

In certain embodiments, the humidity sensor can be integral with thesecond end of the body of the sorbent tube. In additional embodiments,the sorbent tube can include an electrical coupler configured toelectrically couple the humidity sensor to a processor. In someembodiments, the sorbent tube can include at least one coupler on thefirst end of the sorbent tube, the coupler configured to fluidicallycouple the sorbent tube to a purging gas source. In other embodiments,the sorbent tube can include a first sorbent material and a secondsorbent material in the body between the first end and the second end.In some embodiments, a first type of sorbent material is present andcomprises a weaker sorbent strength than a second type of sorbentmaterial that is present. In certain examples, the first type of sorbentmaterial can be positioned adjacent the first end of the body. In otherexamples, the second end of the body can be further configured to coupleto a temperature sensor. In additional examples, the sorbent tube caninclude a heat shielding material in the second end of the sorbent tube.In some examples, the sorbent tube can include a switching valve in oneof the first end and the second end.

In another aspect, a system comprising a purging gas source comprising acoupler configured to provide fluidic coupling between one end of asorbent tube and the purging gas source, and a humidity sensorconfigured to couple to another end of the sorbent tube and to receivefluid from the sorbent tube to detect water levels in the received fluidis provided.

In certain examples, the system can include a receptacle configured toreceive the sorbent tube and to couple to the purging gas source and tofluidically couple to the humidity sensor. In some examples, the systemcan include a manifold fluidically coupled to the purging source, themanifold comprising a plurality of outlets each configured tofluidically couple to a sorbent tube. In other examples, the system caninclude a processor electrically coupled to the humidity sensor. Incertain embodiments, the system can include a manifold fluidicallycoupled to the humidity sensor, in which each port of the manifold isalso fluidically coupled to a single sorbent tube. In some embodiments,the system can include a plurality of humidity sensors each configuredto fluidically couple to a single sorbent tube. In additionalembodiments, the system can include a manifold fluidically coupled tothe purging gas source, the manifold comprising a plurality of outletseach configured to fluidically couple to a sorbent tube. In someexamples, the system can include at least one temperature sensor coupledto the system. In further examples, the system can include a manifoldfluidically coupled to the humidity sensor, in which each port of themanifold is also fluidically coupled to a single sorbent tube. Inadditional examples, the system can include a processor electricallycoupled to the plurality of humidity sensors and the temperature sensor.

In another aspect, a system comprising purging gas source, a receptacleconfigured to receive at least one sorbent tube and fluidically coupledto the purging gas source, and a humidity sensor fluidically coupled tothe receptacle and configured to receive fluid from the receptacle todetect water levels in the received fluid is described.

In certain embodiments, the purging gas source can be coupled to aplurality of receptacles each configured to receive at least one sorbenttube. In other embodiments, the receptacle can be configured to receivetwo parallel sorbent tubes. In further embodiments, the receptacle canbe configured to receive two sorbent tubes in series. In someembodiments, the system can include a manifold fluidically coupled tothe purging source, the manifold comprising at least one outletconfigured to fluidically couple to the receptacle. In other examples,the system can include a processor electrically coupled to the humiditysensor. In further examples, the system can include a manifoldfluidically coupled to the humidity sensor, in which each port of themanifold is also fluidically coupled to a single sorbent tube. Inadditional examples, the system can include a plurality of humiditysensors each configured to fluidically couple to a single sorbent tube.In certain examples, the system can include a processor electricallycoupled to each of the plurality of humidity sensors. In other examples,the system can include a temperature sensor electrically coupled to theprocessor.

In an additional aspect, a method comprising purging a sorbent tube witha purging gas, detecting a humidity level of fluid exiting the purgedsorbent tube with a humidity sensor fluidically coupled to the sorbenttube, and discontinuing purging of the sorbent tube when the humiditylevel drops below a selected humidity level is disclosed.

In certain embodiments, the method comprises detecting a temperature ofthe exiting fluid using a temperature sensor. In some embodiments, themethod comprises detecting a humidity level change during a first periodof about 0.01% humidity per second or less. In other embodiments, themethod comprises detecting a humidity level change during a secondperiod of about 0.1% humidity per second. In additional embodiments, themethod comprises detecting a humidity level change during a third periodof about 0.01% humidity per second or less after the detected changeduring the second period and discontinuing purging of the sorbent tubewhen the change during the third period is detected. In some examples,the method comprises discontinuing purging of the sorbent tube when thedetected water level is about 3% relative humidity or less. In certainexamples, the method comprises actuating a valve between the sorbenttube and a purging gas source that provides the purging gas to controlflow of purging gas to the sorbent tube. In additional examples, themethod comprises actuating the valve to the closed position when thedetected humidity level drops below a selected humidity level. In someembodiments, the method includes continuously monitoring the detectedhumidity levels in the exiting fluid. In additional embodiments, themethod includes discretely monitoring the detected humidity levels inthe exiting fluid. In some examples, the method includes simultaneouslypurging a plurality of sorbent tubes with the purging gas. In furtherexamples, the method includes using a single humidity sensor to monitorthe humidity levels in each of the plurality of sorbent tubes. In someembodiments, the method includes using a plurality of humidity sensorseach fluidically coupled to a single sorbent tube to monitor thehumidity level in each of the plurality of sorbent tubes. In someexamples, the method includes addressing each of the plurality ofhumidity sensors. In additional examples, the method includes using atleast one temperature sensor fluidically coupled to fluid exiting atleast one sorbent tube to determine the humidity level.

In another aspect, a method of purging water from a sorbent tubecomprising introducing a purging gas into a sorbent tube, detecting awater level in fluid exiting the sorbent tube with a humidity sensorfluidically coupled to the sorbent tube, and stopping introduction ofthe purging gas into the sorbent tube when the detected water level inthe exiting fluid is below a selected level is provided.

In certain examples, the selected level is configured to be about 3%relative humidity or less. In other examples, the method includesactuating a valve between the purging gas source and the sorbent tube toa closed position when the detected water level in the exiting fluid isbelow the selected level. In additional examples, the method includesswitching off a gas source providing the purging gas when the detectedwater level in the exiting fluid is below the selected level. In furtherexamples, the method includes simultaneously providing the purging gasto a plurality of sorbent tubes.

In an additional aspect, a method of facilitating removal of water froma sorbent tube, the method comprising providing a humidity sensorconfigured to detect water levels in a fluid exiting the sorbent tubeand provided to the humidity sensor is disclosed.

In certain examples, the method comprises discontinuing provision of apurging gas to the sorbent tube when the humidity sensor detects a waterlevel in the fluid exiting the sorbent tube below a selected level. Inadditional examples, the method comprises providing a valve configuredto be placed between a purging gas source and the sorbent tube, thevalve configured to permit flow of purging gas to the sorbent tube inone state and prevent flow of purging gas to the sorbent tube in anotherstate. In other examples, the method comprises providing a processorconfigured to electrically couple to the humidity sensor. In furtherexamples, the method comprises providing a gas manifold configured toprovide fluidic coupling between the sorbent tube and a purging gassource. In some examples, the method comprises providing a receptacleconfigured to receive the sorbent tube and provide fluidic couplingbetween a purging gas source and the sorbent tube. In additionalexamples, the method comprises providing a plurality of humidity sensorseach configured to fluidically couple to a single sorbent tube to detectwater levels in the fluidically coupled sorbent tube. In certainexamples, the method comprises providing a plurality of receptacles eachconfigured to receive at least one sorbent tube, in which each of theplurality of receptacles is fluidically coupled to one of the pluralityof humidity sensors. In some examples, the method comprises providing atemperature sensor. In other examples, the method comprises providing aninstrument configured to couple to the sorbent tube and to detectspecies eluting from the sorbent tube.

In another aspect, a kit comprising a sorbent tube and a humidity sensoris disclosed. In certain examples, the humidity sensor can be configuredto detect water levels in fluid exiting the sorbent tube. In otherexamples, the kit can include a temperature sensor. In certainembodiments, the kit can include a gas manifold configured to couple thesorbent tube to a purging gas source. In some embodiments, the kit caninclude a receptacle configured to receive the sorbent tube. Inadditional embodiments, the kit can include a plurality of receptacleseach configured to receive at least one sorbent tube. In otherembodiments, the kit can include a plurality of humidity sensors. Insome examples, the kit can include a plurality of sorbent tubes. Infurther examples, the kit can include providing instructions for usingthe plurality of humidity sensors to purge the plurality of sorbenttubes of water. In some examples, the kit can include instructions forusing the humidity sensor to purge the sorbent tube of water.

Additional features, aspects and examples are described in more detailbelow.

BRIEF DESCRIPTION OF THE FIGURES

Certain illustrative embodiments are described in more detail below withreference to the accompanying figures in which:

FIG. 1 graphically illustrates detection of humidity levels in a sorbenttube, in accordance with certain examples;

FIGS. 2A and 2B are illustrations of devices comprising a humiditysensor for detecting humidity levels, in accordance with certainexamples;

FIG. 2C is an illustration of a device comprising two humidity sensors,in accordance with certain examples;

FIGS. 3A and 3B are illustrations of a device comprising a humiditysensor that is fluidically coupled to a sorbent tube, in accordance withcertain examples;

FIGS. 4A and 4B are illustrations showing two sorbent tubes fluidicallycoupled to a humidity sensor through a valve, in accordance with certainexamples;

FIG. 5 is an illustration of a receptacle configured to receive twosorbent tubes in series, in accordance with certain examples;

FIG. 6 is an illustration of a receptacle configured to receive twosorbent tubes in parallel, in accordance with certain examples;

FIG. 7A is an illustration of a receptacle with a common fluid flow pathand FIG. 7B is an illustration of a receptacle with separated fluid flowpaths, in accordance with certain examples;

FIG. 8 is a top view of a device configured to receive four sorbenttubes for purging, in accordance with certain examples;

FIG. 9 is a top view of a device configured to receive six sorbent tubesfor purging, in accordance with certain examples;

FIGS. 10A and 10B are block diagrams of systems comprising a purging gassource, a humidity sensor and a processor, in accordance with certainexamples;

FIG. 11 is an illustration of a system comprising a single humiditysensor and a plurality of sorbent tubes, in accordance with certainexamples;

FIG. 12 is an illustration of a system comprising a plurality ofhumidity sensors and a plurality of sorbent tubes, in accordance withcertain examples;

FIG. 13 is a block diagram of steps that can be used to purge a sorbenttube, in accordance with certain examples;

FIG. 14 is a circuit diagram of a system used to purge sorbent tubes, inaccordance with certain examples;

FIG. 15 is an illustration of a system used to purge sorbent tubes, inaccordance with certain examples; and

FIG. 16 is a graph of relative humidity versus time in seconds for asorbent tube that included about 35 mg of water by weight, in accordancewith certain examples.

It will be recognized by the person of ordinary skill in the art, giventhe benefit of this disclosure, that the relative positions and sizes ofthe components in the figures are not limiting and that no particularsize, dimension, thickness or arrangement is implied as being requiredbased on the representations of the components shown in the figures.

DETAILED DESCRIPTION

In the illustrative embodiments described below, certain components areincluded in the devices and systems. Depending on the desiredconfiguration of the device, it may be desirable to include additionalcomponents, omit one or more components or rearrange or substitute othercomponents into the devices and systems.

In certain embodiments, the devices, systems and methods describedherein can be used to purge sorbent tubes of adsorbed water or to loadtubes with a desired amount of water. Purging can be performed priorloading the tube with sorbent material, after loading the tube withsorbent material but before exposure of the sorbent tube to analyte,after loading the tube with sorbent material and after exposure of thesorbent tube to analyte but before analysis of the analyte, or at othertimes. While the terms “purge” and “purging” are used in certaininstances herein, these terms are not intended to mean that all water isremoved from the tube. Instead, purging can be performed until a desiredlevel of water is achieved, which may be substantially zero or can besome other selected water level if desired. In some examples, thedevices, systems and methods provided herein can be used to load thesorbent material of the sorbent tube with a desired level of water priorto exposure of the sorbent tube to one or more analytes. By loading thetube with a desired amount of water, the tube can be tuned or used as afilter to prevent or reduce adsorption of certain species that may bepresent in a sample, e.g., polar species. Additional uses of thedevices, systems and methods disclosed herein are provided in moredetail below.

Thermal desorption (TD) is commonly used for the determination of traceorganics in air, when using in conjunction with gas chromatography/ormass spectrometry or combinations thereof. The technique can concentratethese analytes many orders of magnitude but also concentrates water aswell. The water levels can be as high as 35 mg loading on a standardthermal desorption tube also referred to herein in certain instances asa sorbent tube. This water can affect both the chromatography of theanalytes as well as suppress responses. In order to reduce the effect ofwater, it is possible to either dry purge the tube or use alternatesampling strategies such as passing the sample through a Nafion® dryer.The Nafion® dryer can be effective at removing water but can also removepolar compounds as well. The principle of dry purging is to pass carriergas in the sampling direction to remove water from hydrophobic sorbentssuch as the Carbon Molecular Sieves (CMS). It is difficult, however topredict how much water is on the sorbent tube. As such, purging of thetubes is usually done for excessive times to ensure all water has beenremoved. Drawbacks exist to excessive purging including the loss ofultra volatile gases that may be present as well as increased andunnecessary analytical time due to the excessive purging.

In certain embodiments, the devices and systems described herein can usereduced levels of purging gases to provide a desired level of water in asorbent tube. In some embodiments, purging may be automatically haltedor stopped once the water level reaches a desired level. Such automatichalting or stopping can be performed, for example, by discontinuingprovision of a purging gas to a sorbent tube once or as soon as thedesired water level is detected. In other embodiments, the devices andsystems described herein can be used to load a sorbent tube with adesired amount of water. As discussed elsewhere herein, loading of thesorbent tube with certain levels of water can provide for tuning of thesorbent tube to prevent (or reduce) substantial adsorption of certainspecies by the sorbent material in the tube.

In certain embodiments, the systems, devices and methods disclosedherein can be used to reduce levels of water in a sorbent tube atambient temperature, e.g., about 23-25° C., at a temperature aboveambient temperature or at a temperature below ambient temperature. Insome examples, a correction factor can be used to account for anyvariations in humidity measurements with temperature. Such correctionfactor can be based on the actual temperature used to purge the tubes,e.g., as detected with an internal or external temperature sensor orthermometer. In some instances, the system can include a heater, cooleror both such that temperature is fixed and any calibration of thehumidity sensor can be based on the operating temperature of the system.If desired, the temperature of the purging gas can be controlled ormatched to the temperature of the system such that purging gas flowswith a different temperature do not alter the humidity measurements. Insome embodiments, only the sorbent tube to be purged can be heated orcooled, whereas in other embodiments, the entire apparatus that hold thesorbent tube may be exposed to heat or cooling. If desired, the systemcan be heated or cooled for a desired period so that temperatureequilibration may occur prior to any humidity measurements. In someexamples, the system can be configured to implement a delay time priorto initiation of humidity measurement and/or introduction of a purginggas such that the sorbent tube can reach the desired temperature.

In certain examples, FIG. 1 graphically illustrates a humidity responseof a sorbent tube as a function of time. In a typical purging operation,a gas is introduced into the sorbent tube. In some examples, the gas maybe an inert gas such as, for example, nitrogen, hydrogen, helium, argon,dry air, carbon dioxide or other gases that generally would not reactwith analyte to any substantial degree under the analytical conditions.Illustrative flow rates for the purging gas (or the loading gas ininstances where the gas is used to add water to a sorbent tube) can varyfrom about 10 mL/minute to about 500 mL/minute, e.g., about 100-200mL/minute. The flow rate of the gas can vary depending on the nature ofthe gas, and different flow rates can result in shifting of the detectedhumidity levels, e.g., shifting of the curve of FIG. 1 left or right.The particular pressure selected can also vary, and the pressureselected desirably retains higher gas capacity to remove any water fromthe sorbent tube.

As shown in FIG. 1, an unpurged tube generally has high levels of wateradsorbed to the sorbent material. The particular water level can varyfrom tube to tube and can be, for example, 35 mg or more or, in otherinstances, can be less than 35 mg of water, e.g., 10 mg, 5 mg or a fewmg of water. As purging gas is introduced into the sorbent tube, waterdesorbs from or diffuses out of the sorbent material and becomesentrained in the purging gas. The purging gas comprising the water exitsthe sorbent tube where it can be detected with a humidity sensor orother suitable sensor including electrochemical sensors and electrodes.As shown in FIG. 1, during a first period 110, the humidity levelremains substantially constant. In mathematical terms for the timebetween t₁ and t₂,

$\frac{d\left\lbrack {{humidity}\mspace{14mu}{level}} \right\rbrack}{dt} \approx {0\mspace{14mu}{for}\mspace{14mu} t_{1}\mspace{14mu}{through}\mspace{14mu} t_{2}}$for the first period 110. In some instances, the slope, e.g., change inhumidity level, may be negative 0.01% humidity per second or lessbetween times t₁ and t₂. As purging gas flows through the sorbent tube,at time t₂ a rapid decrease in the humidity level is observed during theperiod 120. In mathematical terms for successive periodic intervalswithin t₂ and t₃ of the second period 120,

$\frac{d\left\lbrack {{humidity}\mspace{14mu}{level}} \right\rbrack}{dt} \neq {0\mspace{14mu}{for}\mspace{14mu} t_{2}\mspace{14mu}{through}\mspace{14mu} t_{3}}$with the slope during the period 120 being substantially negative. Incertain examples, the absolute magnitude of the slope between periods t₂and t₃ may be substantially larger, e.g., 10× greater, than the slopebetween times t₁ and t₂. For example, the slope between times t₂ and t₃may be −0.1% humidity per second or higher in absolute magnitude, e.g.,−0.2% humidity per second or more. At time t₃, substantially all waterhas been purged from the sorbent tube and the change in humidity levelsfrom time t₃ to time t₄ is about zero as little or no amounts of waterremain in the sorbent tube. The change in slope during a third period130 from time t₃ to t₄ may be similar to that observed during the firstperiod 110, e.g., the slope may be −0.01% humidity per second. Incertain embodiments of the devices and systems described herein, thedetection of the large change in slope magnitude, e.g., the slope changeduring the period 120, can be used to determine when purging iscomplete. For example, detection of a large change in slope followed bylittle or no change in slope can be used to determine when purging issubstantially complete. In some instances, subsequent detection ofsubstantially no change in slope followed by detection of a large slopechange can be used as an indicator or inflection point of substantiallycomplete purging of the sorbent tube. In certain embodiments, once thelarge slope change is observed, purging may be discontinued as soon asthe change in slope approaches about zero, e.g., at the beginning of theperiod 130 at time t₃.

In other instances, purging of the sorbent tube may be consideredcomplete when the humidity level drops below a desired level. In suchconfigurations, continuous monitoring of the purging may or may not beimplemented. Instead, once the measured humidity drops below a selectedlevel, then purging of the sorbent tube may be considered complete. Ininstances where the desired level of humidity is used to determine whenpurging is complete, purging may be monitored at periodic or discreteintervals. For example, humidity levels may be continuously monitoredsubsequent to introduction of a purging gas, humidity levels may bemonitored after a delay period, e.g., 500 seconds or more, humiditylevels may be monitored incrementally or other monitoring times andintervals can be selected. In some embodiments, where a single humiditysensor is used with a plurality of sorbent tubes, it may be desirable tomonitor each sorbent tube incrementally such that humidity levels forall tubes can be measured using the single humidity sensor.

In certain embodiments, a device suitable for detecting humidity levelsis shown in FIG. 2A. The device 200 comprises a receptacle 205configured to receive a sorbent tube. The receptacle 205 is generallysized and arranged to receive a sorbent tube and may have dimensionslarger than the sorbent tube to ensure the entire sorbent tube can beplaced in the receptacle 205. In some embodiments, a friction fit mayexist between the sorbent tube and the receptacle 205 such that purginggas is forced through the sorbent tube to exit the receptacle 205. Inother instances, a gasket may exist such that purging gas is forcedthrough the sorbent tube to exit the receptacle 205. In other instances,purging gas can be provided to the receptacle 205 and can enter thesorbent tube 205 and other portions of the receptacle 205. The device200 also comprises a fluid conduit or connection 210 to permit couplingof the receptacle 205 to a fluid line that provides a purging gas. Ahumidity sensor 220 can be positioned downstream of the receptacle 205(FIG. 2A) in a fluid outlet 215 of the receptacle 205 so that the fluidstream exiting the sorbent tube in the receptacle 205 is provided to thehumidity sensor 220 for detection of the water levels in the fluidstream.

In certain embodiments, the humidity sensor can be positioned at otherareas relative to the positioning of the sorbent tube in the receptacle.For example and referring to FIG. 2B, a device 230 comprising a humiditysensor 240 positioned in a receptacle 235 is shown. Referring to FIG.2C, a device 250 comprising a first humidity sensor 260 in a receptacle255 and a second humidity sensor 265 in a fluid outlet of the receptacle255 is shown. The use of more than a single humidity sensor can providefor increased accuracy. In addition, where two or more humidity sensorsare present, the humidity sensors can be the same or can be different.For example, it may be desirable to select a first humidity sensorhaving a fast response time but low sensitivity to determine initialhumidity levels. The second humidity sensor can be selected to be moreaccurate than the first humidity sensor and used to determine moreprecise levels of water in the sorbent material. More than two humiditysensors can also be present in the devices and systems described herein.Optionally, one or more temperature sensors (not shown) can be presentin the devices 200, 230 and 250 to compensate for humidity leveldeviations due to changes in temperature. Where a temperature sensor ispresent, it may be present upstream of the humidity sensor or downstreamof the humidity sensor. In some examples, the temperature sensor isadjacent to the humidity sensor to ensure the two sensors are at aboutthe same temperature. In some embodiments, the humidity sensor can beincluded or integrated into its own receptacle or container which can befluidically coupled with the receptacle comprising the sorbent tube.

In certain examples, the devices and systems described herein may omit areceptacle entirely and may be configured to couple directly to the endsof the sorbent tube. For example and referring to FIG. 3A, a sorbenttube 310 is shown as being fluidically coupled to a humidity sensor 315through a fluid conduit 314. The sorbent tube 310 is fluidically coupledto a source of purging gas through a fluid conduit 312. While fluidconduits 312 and 314 are shown as being at opposite ends of the sorbenttube 310 and generally in-line with the sorbent tube 310, one or more ofthe fluid conduits can be positioned at a right angle to the sorbenttube 310 or at another desired angle. Generally, the fluid conduits 312,314 may be coupled to the sorbent tube 310 in any desired orientationthat permits fluid to flow to and from the sorbent tube 310. Each of thefluid conduits 312 and 314 may include a gasket or suitable fittings toprovide a substantially fluid tight seal between the conduits 312 and314 and the ends of the sorbent tube 310. In operation, a purging gas isprovided through the fluid conduit 312, flows through the sorbent tube310 in the direction of arrow 320 and exits the sorbent tube 310 intothe fluid conduit 312. As shown in FIG. 3A, a humidity sensor 325 ispositioned in the fluid conduit 314 and is operative to detect waterlevels in the fluid stream that exits the sorbent tube 310. In addition,one or more temperature sensors may also be present in one or more ofthe fluid conduits 312 and 314 or in the sorbent tube 310 to provide forincreased accuracy in the humidity level measurements.

In certain embodiments, the purging gas may be provided to the fluidflow path within a sorbent tube. For example, the sorbent tube caninclude integral couplings or fittings to provide fluid flow from apurging gas source into the internal fluid flow path of the sorbenttube. An illustration is shown in FIG. 3B. The sorbent tube 350comprises a first fitting 352 and a second fitting 354 on an oppositeend of the sorbent tube 350. A purging gas can be provided from a gassource (not shown) to the first fitting 352 of the sorbent tube 350. Aspurging gas flows through the internal fluid flow path of the sorbenttube 350, adsorbed water desorbs and diffuses into the purging gas as itflows in the general direction of arrow 360. Purging gas with waterexits the sorbent tube 350 through the second fitting 354 where waterlevels can be detected by a humidity sensor 365 in the second fitting354. If desired, the humidity sensor 365 can be positioned external tothe sorbent tube 350, e.g., in a fluid flow line that is fluidicallycoupled to the second fitting 354. In addition, one or more temperaturesensors (not shown) can be present in the sorbent tube 350 or in a fluidline fluidically coupled to the sorbent tube 350. Where sensors arepresent in the sorbent tube 350, they can be added prior to disposal ofsorbent material in the sorbent tube or after disposal of sorbentmaterial in the sorbent tube. Where the sorbent material disposaloperation is performed at a temperature that may harm the sensor(s), thesensor is desirably added to the sorbent tube after disposal of thesorbent material to the sorbent tube. In embodiments where a humiditysensor is integral to the sorbent tube, the sorbent tube can include oneor more external connectors such that a lead, plug or other device canbe electrically coupled to the external connectors to provide electricalcoupling between the integral sensor and another desired device orsystem, e.g., a display, printer, recorder, processor or the like.

In certain examples, a single humidity sensor can be used with more thana single sorbent tube. For example, to reduce overall cost and to addsimplicity to the device, a single humidity sensor can be present andoperative to receive fluid flow from two or more sorbent tubes.Illustrations are shown in FIGS. 4A and 4 B. The device 400 comprises afluid flow path 405 fluidically coupled to a valve 410. The fluid flowpath 405 comprises a humidity sensor 415 operative to detect waterlevels in fluid. Two sorbent tubes 420 and 430 are each fluidicallycoupled to the valve 410 through fluid flow paths 422 and 432,respectively. The valve 410 is configured with an internal fluid flowpath that can be switched to provide fluidic coupling between thesorbent tube 420 and the humidity sensor 415 (FIG. 4A) or the sorbenttube 430 and the humidity sensor 415 (FIG. 4B). The valve 410 may becycled with a frequency of about 0.1 Hz to about 10 Hz. Where more thantwo sorbent tubes are used with a single humidity sensor, the valve canbe configured to provide sequential fluidic coupling between the varioussorbent tubes and the single humidity sensor. The valve 410 can be a lowcost solenoid valve or other suitable valve that can be switched tofluidically couple two fluid flow paths. In a typical operation, thevalve 410 would be switched to provide fluidic coupling between thesorbent tube 420 and the humidity sensor 415 for a desired period, e.g.,1-10 or 1-100 seconds or more, as shown in FIG. 4A. Levels of water inthe fluid stream received from the sorbent tube 420 would be detectedand used as an indicator of the water level in the sorbent tube 420. Thevalve 410 would then be switched to its second position to providefluidic coupling between the sorbent tube 430 and the humidity sensor415 for a desired period, e.g., 1-10 or 1-100 seconds or more, as shownin FIG. 4B. Levels of water in the fluid stream received from thesorbent tube 430 would be detected and used as an indicator of the waterlevel in the sorbent tube 430. In one alternative mode of operation, thehumidity sensor 415 can be fluidically coupled to the sorbent tube 420until the sorbent tube 420 reaches a desired water level. The valve 410can then be switched to provide fluidic coupling between the sorbenttube 430 and the humidity sensor 415 to permit detection of water levelsin the sorbent tube 430. If desired, the provision of purging gas to thesorbent tube 430 can be delayed for a desired period. In some examples,upstream of the sorbent tubes 420 and 430 may be a gas manifold or gasfittings (not shown) which can provide fluidic coupling between thesorbents tube 420 and 430 and a purging gas source. In measuring fluidstreams from the sorbent tube 420 and 430, the humidity levels can bemeasured using the same channel (or displayed as being overlapping on asingle display or printer) and when the measurements substantiallyoverlap at a desired level, purging may be discontinued. Alternatively,fluid flow from each sorbent tube may be provided to its own discretedetector (or channel thereof) such that humidity levels in the sorbenttubes can be displayed or monitored independently of each other.

In certain examples, the valve 410 can be a solenoid valve or otherinexpensive valve that can be switched at a desired frequency andprovide fluidic coupling (or not depending on the state of the valve)between two or more components of the device. In some examples, thevalve 410 can be configured as a three-way valve or a multi-way valve sothat a single valve can provide fluidic coupling between a plurality ofsorbent tubes and a single humidity sensor. Similarly, a multi-way valvecan be positioned upstream of a plurality of sorbent tubes so thatpurging gas can be selectively provided to one or more sorbent tubes butnot necessarily all sorbent tubes at the same time. Depending on theflow rates used, a swafer device commercially available from PerkinElmerHealth Sciences, Inc. (Waltham, Mass.) can be used to provide purginggas to a desired sorbent tube and/or to provide a fluid stream from aselected sorbent tube to a humidity sensor. Illustrative swafer devicesare described in more detail in commonly owned pending U.S. patentapplication Ser. No. 12/472,948, the entire disclosure of which ishereby incorporated herein by reference for all purposes. In someexamples, the valve 410 can be omitted entirely and fluid exiting fromboth the sorbent tube 420 and the sorbent tube 430 can be providedsimultaneously to the humidity sensor 415. In such a configuration, theoverall signal is representative of average humidity levels in the twosorbent tubes.

In certain embodiments, two or more sorbent tubes can be placed in-lineto purge each of them. An in-line configuration may be desirable forexample to purge the sorbent tubes prior to exposure to any analyte. Anillustration of a device comprising in-line sorbent tubes is shown inFIG. 5. A device 500 comprises a receptacle 505 sized and arranged toreceive two sorbent tubes 510 and 520. The receptacle 505 can befluidically coupled to a purging gas source (not shown) at an end 506and to a humidity sensor 530 at an end 508. The humidity sensor 530 isoperative to detect water levels in fluid exiting the receptacle 505. Apurging gas is provided in the direction of arrow 502, and fluid exitsthe receptacle 505 in the direction of the arrow 504. Such fluidtypically includes water from both the sorbent tubes 510 and 520. Wherethe tubes 510 and 520 are in-line as shown in FIG. 5, water can exit thetube 510 and may become re-adsorbed to the tube 520. Once substantiallyall water exits the tube 510, fluid provided from the tube 510 to thetube 520 will generally be substantially free of water. Water can thenexit from the tube 520 in a manner similar to the profile shown in FIG.1 until substantially all water is removed from the sorbent tube 520.The water levels in both sorbent tubes 510 and 230 can be lowered to adesired level or substantially all water can be removed from both thesorbent tubes 510 and 520. While the receptacle 505 is shown as beingsized and arranged to receive two sorbent tubes 510 and 520, the sizecan be altered such that more than two sorbent tubes can be placed intothe receptacle 505. For example, the receptacle 505 can be configured toreceive three sorbent tubes, four sorbent tubes, five sorbent tubes ormore than five sorbent tubes in an in-line configuration similar to thatshown in FIG. 5. Where the receptacle 505 is sized and arranged toreceive multiple sorbent tubes, the receptacle 505 need not be filledwith or occupied by the total number of sorbent tubes it is capable ofreceiving. For example, a receptacle sized and arranged to receive fivesorbent tubes can be used to purge less than five sorbent tubes, e.g.,one, two, three, or four two sorbent tubes, of water. While the device500 is shown in a horizontal position in FIG. 5, it can be used in avertical position with one of the sorbent tubes 510 and 520 restingagainst an end 506 or 508 of the receptacle 505, and the other sorbenttube can be in direct physical contact with the first sorbent tube. Ifdesired, the sorbent tubes can be configured with bosses or spacers atthe ends to provide a desired separation between the two sorbent tubes.

In certain examples, two or more sorbent tubes can be placed in a commonfluid flow path but not necessarily in-line. One illustration of stackedsorbent tubes is shown in FIG. 6. The device 600 comprises a receptacle605 comprising a first compartment 615 configured to receive a sorbenttube 625 and a second compartment 620 configured to receive a sorbenttube 635. A common fluid flow path 617 is provided such that purging gasintroduced into the receptacle 605 can be provided to both the sorbenttubes 625 and 635. A humidity sensor 640 is positioned at an end of thereceptacle 605 where fluid exits from the receptacle 605. The humiditysensor 640 is operative to detect water levels in the exiting fluid. Thedevice 600 can include a removable top or end so that the sorbent tubes625 and 635 can be added to the compartments 615 and 620, respectively.While the sorbent tubes 625 and 635 are shown positioned toward one endof the receptacle 605, the sorbent tubes can be positioned anywherewithin the compartments 615 and 620. Where the device 600 is orientedvertically with the humidity sensor 640 positioned at the base of thedevice 600, the sorbent tubes 625 and 635 may be positioned as shown inFIG. 6 due to gravity. In operation of the device 600, purging gas isprovided to both sorbent tubes 625 and 635 simultaneously. Fluid exitingthe sorbent tubes 625 and 635 is provided in combination to the humiditysensor 640, which is operative to detect water levels in the fluid. Whenthe overall level of water reaches a desired level, the purgingoperation may be stopped and the sorbent tubes 625 and 635 can beremoved for analysis, or where the purging is performed prior toexposure to analyte, the sorbent tubes 625 and 635 can be used to sampleanalyte. Devices configured with multiple compartments to hold more thantwo sorbent tubes can be constructed and used in a similar manner to thedevice 600. For example, a device comprising a common fluid flow paththat is configured to receive, three, four, five or more sorbent tubescan be provided and used to purge each of the sorbent tubes in thedevice. Where a device comprising a plurality of compartments isavailable, a sorbent tube need not be present in every compartment forthe device to work properly.

In certain embodiments, the devices described herein can include ahumidity sensor for each compartment or sorbent tube to be purged. Oneillustration is shown in FIG. 7A. The device 700 comprises a firstcompartment 710 and a second compartment 715. A sorbent tube 720 is inthe first compartment 710 and a sorbent tube 725 is in the secondcompartment 715. The first compartment 710 and the second compartment715 may each include suitable internal positioners, bosses or fitting toposition the sorbent tubes 720 and 725 at a desired position within thecompartments 710 and 715, respectively. Alternatively, the compartments710 and 715 may have a variable diameter so that the sorbent tubes 725and 735 are placed in them and a friction fit is created between thesorbent tube and the wall of the compartment. A first humidity sensor730 is fluidically coupled to the sorbent tube 720, and a secondhumidity sensor 735 is fluidically coupled to the sorbent tube 725. Thehumidity sensors 730 and 735 function independently of each other andeach are electrically coupled to a processor, display, printer or othersimilar devices, which may be the same or different, e.g., one humiditysensor can be coupled to a display and the other humidity sensor can becoupled to printer. In some examples, each humidity sensor can beelectrically coupled to its own processor, display, printer or the like.The humidity sensors 730 and 735 can include an address or beaddressable so that the particular water level in a particular sorbenttube can be easily determined. In certain examples, the device 700 caninclude more than two compartments. For example, the device 700 can beconfigured with three or more compartments each configured to receive asingle sorbent tube. Where more than two compartments are present, eachcompartment desirably is fluidically coupled to its own humidity sensor.In other examples, each compartment and/or associated humidity sensorcan be individually addressed so that a user can identify whichparticular sorbent tube is associated with a displayed or detected waterlevel.

In certain examples where two or more sorbent tubes that are eachfluidically coupled to its own humidity sensor are present, the fluidflow path that provides purging gas may be separated so that nointer-sorbent tube contamination may occur. One such illustration isshown in FIG. 7B. The device 750 comprises two separated compartments755 and 760 comprising a sorbent tube 765 and 770, respectively. Purginggas can be provided upstream to each of the compartments 755 and 760such that no fluid flow path exists between the two compartments 755 and760. By separating out the compartments 755 and 760, unwanted analytetransfer between sorbent tubes should not occur. The sorbent tube 765 isfluidically coupled to a humidity sensor 775, and the sorbent tube 770is fluidically coupled to a humidity sensor 780. The humidity sensors775 and 780 function independently of each other and each can beelectrically coupled to a processor, display, printer or other similardevices, which may be the same or different. In some examples, eachhumidity sensor can be electrically coupled to its own processor,display, printer or the like. The humidity sensors 775 and 780 caninclude an address or be addressable so that the particular water levelin a particular sorbent tube can be easily determined. In certainexamples, the device 750 can include more than two compartments. Forexample, the device 750 can be configured with three or morecompartments each configured to receive a single sorbent tube. Wheremore than two compartments are present, each compartment desirably isfluidically coupled to its own humidity sensor. In other examples, eachcompartment and/or associated humidity sensor can be individuallyaddressed so that a user can identify which particular sorbent tube isassociated with a displayed or detected water level.

In examples of the devices and systems where a processor is present, theprocessor can be any suitable commercially available processor.Similarly, numerous different types of humidity sensors, such as thosecommercially available from Honeywell Industries, can be used. Ifdesired, the humidity sensor and/or processor can be selected from thoseable to withstand high temperatures commonly encountered in gaschromatographic (GC) techniques such that the sensor and/or processorcan be integrated into the sorbent tube and not destroyed by the hightemperatures. In other configurations, an inexpensive processor and/orsensor can be selected such that they are destroyed during the GCtechniques from the high temperatures. In other configurations, thehumidity sensor and/or processor may not be exposed to high temperaturesand can be reused for additional sorbent tubes.

In certain embodiments where more than two compartments are present, thedevice can be configured in a block configuration, circular, e.g., in acarousel, or in other shapes and configurations. Referring to FIG. 8, atop view of a block configuration of a device 800 is shown whichincludes four compartments 805, 810, 815 and 820. Each of thecompartments 805, 810, 815 and 820 is sized and arranged to receive atleast one sorbent tube, though the exact dimensions of each compartmentneed not be exactly the same as the other compartments. In someexamples, each of the compartments 805, 810, 815 and 820 is fluidicallycoupled to its own respective humidity sensor, whereas in otherexamples, fewer than four humidity sensors can be present in the device800. For example, two humidity sensors can be present with one humiditysensor being configured to fluidically couple to the compartments 805and 810 and the other humidity sensor being configured to fluidicallycouple to the compartments 815 and 820. In other embodiments, one orthree humidity sensors can be used with the device 800. Each humiditysensor can be individually controlled so that the water level in eachsorbent tube can be detected. The device 800 can couple to a manifold orcoupler (not shown) that is configured to provide a purging gas to thecompartments 805, 810, 815 and 820. Gaskets or sealing members can beincluded between the coupler and the device 800 so that a substantiallyfluid tight seal is provided between them. Referring to FIG. 9, a topview of a carousel configuration is shown. The device 900 comprises ahousing 910 having a generally circular cross-section comprising aplurality of compartments 915, 920, 925, 930, 935 and 940 eachconfigured to receive at least one sorbent tube (not shown). In someembodiments, each of the compartments 915, 920, 925, 930, 935 and 940 isfluidically coupled to its own respective humidity sensor, whereas inother examples, fewer than six humidity sensors can be present in thedevice 900, e.g., five, four, three, two or one humidity sensor can bepresent. Each humidity sensor present in the device 900 can beindividually controlled so that the water level in each sorbent tube canbe detected. The device 900 can couple to a manifold or coupler (notshown) that is configured to provide a purging gas to the compartments915, 920, 925, 930, 935 and 940. Gaskets or sealing members can beincluded between the coupler and the device 900 so that a substantiallyfluid tight seal is provided between them.

In certain examples, the devices described herein can be used in asystem that comprises a purging gas and a processor. A block diagram ofa system is shown in FIG. 10A. The system 1000 comprises a purging gassource 1010 fluidically coupled to a device 1020 configured to receiveat least one sorbent tube, such as those illustrative devices describedherein. The system 1000 also include a humidity sensor 1030 fluidicallycoupled to the device 1020. The humidity sensor 1030 is typicallyelectrically coupled to a processor 1040, though it instead can becoupled to a display, printer, recorder or other devices designed topermit visualization or an indication of water levels detected by thehumidity sensor 1030. In operation of the system 1000, purging gas isprovided from the purging gas source 1010 to the device 1020 configuredto receive at least one sorbent tube. Water levels in fluid exiting thedevice 1020 are detected by the humidity sensor 1030. The humiditysensor 1030 and optionally the purging gas source 1010 can be controlledwith the processor 1040. For example, the processor 1040 can beconfigured to control provision of the purging gas to the device 1020until a desired water level is detected by the humidity sensor 1030. Theprocessor 1040 can then switch off a pump or valve to stop flow orpurging gas to the device 1020. In some embodiments the processor 1040can be part of a larger computer system operative to control the purginggas source 1010 and the humidity sensor 1030.

In certain embodiments, a sorbent tube can be directly coupled to apurging gas source and the device can be omitted. Referring to FIG. 10B,a system 1050 comprises a purging gas source 1060 fluidically coupled toa sorbent tube 1070. The sorbent tube 1070 is fluidically coupled to ahumidity sensor 1080, which is electrically coupled to a processor 1090.In operation of the system 1050, purging gas is provided from thepurging gas source 1060 to the sorbent device 1070. Water levels influid exiting the sorbent tube 1070 are detected by the humidity sensor1080. The humidity sensor 1080 and optionally the purging gas source1060 can be controlled with the processor 1090. For example, theprocessor 1090 can be configured to control provision of the purging gasto the sorbent tube 1070 until a desired water level is detected by thehumidity sensor 1080. The processor 1090 can then switch off a pump orvalve to stop flow or purging gas to the sorbent tube 1070. In someembodiments the processor 1090 can be part of a larger computer systemoperative to control the purging gas source 1060 and the humidity sensor1080.

In certain examples, a system comprising a single humidity sensor andconfigured to receive fluid flow from a plurality of sorbent tubes canbe used to determine the water level in each of the sorbent tubes.Referring to FIG. 11, a system 1100 comprises a gas manifold 1120fluidically coupled to a purging gas source (not shown). The gasmanifold 1120 provides a purging gas to each of sorbent tubes 1130,1132, 1134 and 1136. Each of the sorbent tubes 1130, 1132, 1134 and 1136is fluidically coupled to a valve 1140, 1142, 1144 and 1146,respectively. The valves 1140, 1142, 1144 and 1146 can be independentlyactuated to open and closed positions such that fluid flow from a singlesorbent tube (or multiple sorbent tubes) is provided to a humiditysensor 1160 through a gas manifold 1150. In some examples, only a singlevalve is open to the humidity sensor 1160 during any period, whereas inother examples, two, three or four of the valves 1140, 1142, 1144 and1146 can be open to the humidity sensor 1160. The humidity sensor 1160is typically coupled to a processor (not shown) that can receive signalsfrom the humidity sensor 1160 to determine water levels in the fluidprovided to the humidity sensor 1160. The valves 1140, 1142, 1144 and1146 can be coupled to the same processor as the humidity sensor 1160 orcan be coupled to a different processor. The processor can be configuredto open one or more of the valves 1140, 1142, 1144 and 1146 to provide adesired fluid flow to the humidity sensor 1160. In certain examples,additional valves can be present between the gas manifold 1120 and thesorbent tubes 1130, 1132, 1134 and 1136 such that purging gas can beindependently provided (or shut off) to any one or more of the sorbenttubes 1130, 1132, 1134 and 1136. Such additional valves can beintegrated into the gas manifold 1120 or can be separate from it.Similarly, the valves 1140, 1142, 1144 and 1146 can be integrated intothe gas manifold 1150 if desired. In some embodiments, the sorbent tubes1130, 1132, 1134 and 1136 can be positioned in receptacles (not shown)that are between the gas manifold 1120 and the valves 1140, 1142, 1144and 1146. As discussed herein, the receptacle can be configured toreceive a single sorbent tube or two or more sorbent tubes, e.g., inseries or in parallel, if desired. In certain examples, one or moretemperature sensors (not shown) can be present in the system 1100 toaccount for the variations in the humidity levels based on the measuredtemperature.

In some examples, a system that includes a humidity sensor for eachrespective sorbent tube can be used to detect water levels separately ineach of the sorbent tubes. Referring to FIG. 12, a system 1200 comprisesa gas manifold 1220 fluidically coupled to a purging gas source (notshown). The gas manifold 1220 provides a purging gas to each of sorbenttubes 1230, 1232, 1234 and 1236. Each of the sorbent tubes 1230, 1232,1234 and 1236 is fluidically coupled to a valve 1240, 1242, 1244 and1246, respectively. The valves 1240, 1242, 1244 and 1246 can beindependently actuated to open and closed positions such that fluid flowfrom a single sorbent tube (or multiple sorbent tubes) is provided to arespective humidity sensor 1250, 1252, 1254 and 1256. In some examples,only a single valve is open to its respective humidity sensor during anyperiod, whereas in other examples, two, three or four of the valves1240, 1242, 1244 and 1246 can be open to its respective humidity sensor1250, 1252, 1254 and 1256. The humidity sensors 1250, 1252, 1254 and1256 are each typically coupled to a processor (not shown) that canreceive signals from the humidity sensors 1250, 1252, 1254 and 1256 todetermine water levels in the fluid provided to the humidity sensors1250, 1252, 1254 and 1256. If desired, each of the humidity sensors1250, 1252, 1254 and 1256 can be electrically coupled to its owndedicated processor. In some examples, the humidity sensors 1250, 1252,1254 and 1256 and/or sorbent tubes 1230, 1232, 1234 and 1236 can beaddressed or addressable such that the particular water level detectedby the processor can be associated with a particular sorbent tubepresent in the system 1200. In some embodiments, the valves 1240, 1242,1244 and 1246 can be coupled to the same processor as the humiditysensors 1250, 1252, 1254 and 1256 or can be coupled to a differentprocessor. The processor can be configured to open one or more of thevalves 1240, 1242, 1244 and 1246 to provide a desired fluid flow to thehumidity sensors 1250, 1252, 1254 and 1256. In certain examples,additional valves can be present between the gas manifold 1220 and thesorbent tubes 1230, 1232, 1234 and 1236 such that purging gas can beindependently provided (or shut off) to any one or more of the sorbenttubes 1230, 1232, 1234 and 1236. Such additional valves can beintegrated into the gas manifold 1220 or can be separate from it.Similarly, the valves 1240, 1242, 1244 and 1246 can be integrated into agas manifold (not shown) if desired. In some embodiments, the sorbenttubes 1230, 1232, 1234 and 1236 can be positioned in receptacles (notshown) that are between the gas manifold 1220 and the valves 1240, 1242,1244 and 1246. As discussed herein, the receptacle can be configured toreceive a single sorbent tube or two or more sorbent tubes, e.g., inseries or in parallel, if desired. In certain examples, one or moretemperature sensors (not shown) can be present in the system 1200 toaccount for the variations in the humidity levels based on the measuredtemperature.

In certain embodiments, a method of purging a sorbent tube of water canbe used to remove the water from a sorbent tube to a desired level.Referring to FIG. 13, the method can include introducing a purging gasinto a sorbent tube at a step 1310 and detecting a humidity level at astep 1320. If the detected humidity level 1320 is below a selectedlevel, then purging can be discontinued at a step 1330. If the detectedhumidity level is above a selected level, the purging gas can continueto be introduced into the sorbent tube at a step 1310 until a desiredhumidity level is reached and purging discontinued at step 1330. Toincrease overall accuracy of the detected humidity levels, a temperaturecan be detected and used to provide a correction factor for the humiditylevel. In some embodiments, introduction of the purging has during step1310 can be continued as long as the humidity level changes by about0.01% humidity per second or less. In certain examples, after detectionof a humidity level change of about 0.1% humidity per second or more,the introduction of the purging gas can be discontinued at step 1330. Insome examples, purging is not discontinued until after detection of ahumidity level change of about 0.1% humidity per second or more followedby detection of a humidity level change of about 0.01% humidity persecond. This plateau, decline, plateau phenomenon would be similar tothat described in reference to FIG. 1 herein. In other examples, purgingis not discontinued at step 1330 until a particular level of water isdetected, e.g., about 3% relative humidity or less. While not shown inthe process steps, the humidity sensor can be calibrated using fluidcomprising a known amount of water so that a calibration curve can beconstructed and used to determine the particular water level in fluidexiting a sorbent tube. Alternatively, the humidity sensor can bepre-calibrated so that its response is known and the user need notcalibrate it prior to use.

In some embodiments, purging can be discontinued by switching off thepurging gas source so that no additional gas is provided to the sorbenttube, whereas in other examples, a valve can be switched to a closedposition so that no additional purging gas is provided to the sorbenttube. In other examples, a vent line can be opened such that purging gasflows out of the system and is not substantially provided to the sorbenttube. In certain examples, the humidity can be monitored continuously sothat humidity levels are measured in real time from the beginning ofintroduction of a purging gas until a desired water level is reached. Inother examples, the humidity can be monitored at discrete times, e.g.,every 10 seconds, 20 seconds, 30 seconds, 1 minute or other selectedintervals. In embodiments where a plurality of sorbent tubes are presentand used with a single humidity sensor, it may be desirable todiscretely monitor each sorbent tube and stagger the monitoring so thatwater levels in fluid from each tube can be detected with greateraccuracy. Even where a plurality of humidity sensors are present,however, discrete monitoring can be performed if desired.

In certain embodiments, a method of facilitating removal of water from asorbent tube comprises providing a humidity sensor configured to detectwater levels in a fluid exiting the sorbent tube and provided to thehumidity sensor. In some embodiments, the humidity sensor can bepre-configured with desired sampling times or other parameters such thata user couples the humidity sensor to a sorbent tube but need nototherwise configure it. In some instances, the method can includeproviding a valve configured to be placed between a purging gas sourceand the sorbent tube, the valve configured to permit flow of purging gasto the sorbent tube in one state and prevent flow of purging gas to thesorbent tube in another state. In certain examples, the method caninclude providing a processor configured to electrically couple to thehumidity sensor. In some embodiments, the method can include providing agas manifold configured to provide fluidic coupling between the sorbenttube and a purging gas source. If desired, a similar gas manifold canalso be provided to couple the sorbent tube to one or more humiditysensors. In some embodiments, the method can include providing areceptacle configured to receive the sorbent tube and provide fluidiccoupling between a purging gas source and the sorbent tube. In certainexamples, a plurality of humidity sensors each configured to fluidicallycouple to a single sorbent tube to detect water levels in thefluidically coupled sorbent tube can be provided. In other examples, aplurality of receptacles each configured to receive at least one sorbenttube, in which each of the plurality of receptacles is fluidicallycoupled to one of the plurality of humidity sensors can be provided. Ifdesired, a temperature sensor can be provided. Alternatively, thehumidity sensor can be calibrated for measurements at a certaintemperature or temperature range so that no temperature sensor need bepresent.

In some embodiments, the method can include providing an instrumentconfigured to couple to the sorbent tube and to detect species elutingfrom the sorbent tube. In certain examples, the instrument can be a gaschromatograph or some other type of fluid chromatograph and may behyphenated to one or more other instruments or detectors, e.g., theinstrument can be a GC-MS. Suitable instruments for detecting speciescommonly adsorbed to sorbent tubes are commercially available fromPerkinElmer Health Sciences, Inc. (Waltham, Mass.). In someconfigurations, the humidity sensor can be placed in-line with theinstrument such that after removal of water analytical measurements canbe initiated. In other configurations, water can be removed to a desiredlevel and then the sorbent tube can be transferred to an instrument fordetection of species adsorbed to the sorbent material in the sorbenttube. In some configurations, the sorbent tube can be in-line with theinstrument, but water exiting the sorbent tube can be detected by thehumidity sensor and vented from the system such that water is notprovided to the chromatographic device or the detector. Once the wateris removed to a desired level, the vent can be closed and sample exitingthe sorbent tube can be provided to the chromatographic device or thedetector. In certain instances, transfer of a purged sorbent tube to aninstrument can be accomplished using autoloading techniques orautoloading devices so that little or no user intervention is requiredonce the sorbent tubes are placed in a suitable device or systemconfigured to purge them of water to a desired level.

In certain examples, the methods, systems and devices disclosed hereincan be used to load sorbent tubes with a desired level of water. Aloading curve would generally by the reverse of that shown in FIG. 1with desired levels of water being detected in fluid exiting the sorbenttube and provided to a humidity sensor. A loading gas can be used andcan include a certain level of water to provide a desired humidity levelto the sorbent tube. This water level can be varied by mixing humidifiedgas with non-humidified gas prior to introduction into the sorbent tube.Where a plurality of sorbent tubes are loaded with water, each of thesorbent tubes need not be loaded to the same level and provision of theloading gas can be stopped once a particular sorbent tube reaches adesired water level.

In certain embodiments, a kit comprising a sorbent tube and a humiditysensor can be used to purge the sorbent tube or load the sorbent tube asdesired. In some embodiments, the humidity sensor can be configured todetect water levels in fluid exiting the sorbent tube. In certainexamples, the kit can include one or more of a temperature sensor, a gasmanifold configured to couple the sorbent tube to a purging gas source,a receptacle configured to receive the sorbent tube, a plurality ofreceptacles each configured to receive at least one sorbent tube, aplurality of humidity sensors, a plurality of sorbent tubes, and/orinstructions for using the humidity sensor or plurality of humiditysensors to purge the plurality of sorbent tubes of water.

The devices, systems and methods described herein can be used with manydifferent types of sorbent tubes including, for example, those describedin commonly owned U.S. patent application Ser. Nos. 12/573,048 and12/729,432, the entire disclosure of each of which is herebyincorporated herein by reference. In brief, a sorbent tube generallyincludes a body comprising one, two or more sorbent materials positionedwithin the body in a suitable manner to adsorb species or analyte in asample. For example, the sorbent tube can include a body comprising asampling inlet, a sampling outlet and a cavity between the inlet and theoutlet, the cavity comprising a serial arrangement of at least twodifferent sorbent materials in which the sorbent materials are arrangedfrom a material with a weakest sorbent strength to a material with astrongest sorbent strength with the weakest sorbent strength materialadjacent to the sampling inlet. In certain examples, the body generallyhas dimensions of about ¼ inches wide by about 3.5-4 inches long.

Certain specific examples are described below to illustrate further someof the novel aspects of the technology described herein.

EXAMPLE 1

A moisture sensor (HIH 5031 commercially available from Honeywell) wasinterfaced to a microprocessor (Arduino Duemilanove commerciallyavailable from Arduino). The HIH 5031 sensor uses 5V input and producesan output voltage that is proportional to the humidity. An Arduinomicroprocessor was used as it is low cost and easy to program/obtain. Inaddition, an Adafruit datalogging shield was used for real timetimekeeping and recording of data to an SD data card. A circuitschematic of the system is shown in FIG. 14 showing the connectionsbetween the processor (ATMega328P) and the other components of thesystem.

A soil vapor tube (SVI commercially available from PerkinElmer HealthSciences, Inc.) was purged with 6 Liters of clean nitrogen at 70%Relative Humidity. The tube was removed and it gained 35 mg of waterwhen weighed on an analytical balance. The tube was attached to a drypurge apparatus as shown in FIG. 15. The system 1500 included a nitrogenpressure regulator 1510 fluidically coupled to a nitrogen gas source(not shown), a metering valve 1520, a plurality of solenoid valves 15301532, 1534, 1536 and 1538 each coupled to a respective sorbent tube1540, 1542, 1544, 1546, and 1548. Suitable solenoid valves arecommercially available from Clippard. Each of the sorbent tubes 1540,1542, 1544, 1546, and 1548 was fluidically coupled to a humidity sensor1550, 1552, 1554, 1556, and 1558 respectively, and the sorbent tube 1548was also fluidically coupled to a temperature sensor 1560.

The time/date/temperature and relative humidity of fluid exiting thesorbent tubes was recorded on a SD memory card. The system 1500 also caninclude an LCD (not shown) to visualize the data. The resulting data wasplotted as shown in FIG. 16, which shows a graph of relative humidityversus time in seconds. Dry nitrogen was used as the purging gas, and apurge flow rate of 100 mL/minute was used.

Once the tube reaches 3% relative humidity (RH), the microprocessor canstop the flow of nitrogen to the sorbent tube by turning off itsrespective solenoid valve. If desired, this signal could also light aLED to signal the operator that the sorbent tube is ready or othervisual indicia can be provided to notify a user that the desired waterlevel has been reached.

A software program written to operate the system of FIG. 15 is providedbelow for convenience purposes only, and additional software programssuitable for controlling the system will be readily selected by theperson of ordinary skill in the art, given the benefit of thisdisclosure.

When introducing elements of the aspects, embodiments and examplesdisclosed herein, the articles “a,” “an,” “the” and “said” are intendedto mean that there are one or more of the elements. The terms“comprising,” “including” and “having” are intended to be open-ended andmean that there may be additional elements other than the listedelements. It will be recognized by the person of ordinary skill in theart, given the benefit of this disclosure, that various components ofthe examples can be interchanged or substituted with various componentsin other examples.

Although certain aspects, examples and embodiments have been describedabove, it will be recognized by the person of ordinary skill in the art,given the benefit of this disclosure, that additions, substitutions,modifications, and alterations of the disclosed illustrative aspects,examples and embodiments are possible.

The invention claimed is:
 1. A method comprising: purging a sorbent tubewith a purging gas; detecting a humidity level of fluid exiting thepurged sorbent tube with a humidity sensor fluidically coupled to thesorbent tube; and discontinuing purging of the sorbent tube when thehumidity level drops below a selected humidity level, wherein thepurging is discontinued when the humidity level drops below 3% relativehumidity and after the humidity sensor detects an inflection point fromdetection of the humidity level of the fluid exiting the purged sorbenttube.
 2. The method of claim 1, further comprising detecting atemperature of the exiting fluid using a temperature sensor.
 3. Themethod of claim 1, further comprising continuing purging of the sorbenttube with the sorbent gas if a detected humidity level change in theexiting fluid is about 0.01% humidity per second or less during a firstperiod.
 4. The method of claim 3, further comprising continuing purgingof the sorbent tube with the sorbent gas when the detected humiditylevel change in the exiting fluid during a second period, after thefirst period, is about 0.1% humidity per second.
 5. The method of claim4, further comprising discontinuing purging of the sorbent tube with thesorbent gas when the detected humidity level change during a thirdperiod, after the second period, is about 0.01% humidity per second orless.
 6. The method of claim 1, further comprising actuating a valvebetween the sorbent tube and a purging gas source that provides thepurging gas to control flow of purging gas to the sorbent tube.
 7. Themethod of claim 6, actuating the valve to the closed position when thedetected humidity level drops below a selected humidity level.
 8. Themethod of clam 1, further comprising continuously monitoring thedetected humidity levels in the exiting fluid.
 9. The method of claim 1,further comprising discretely monitoring the detected humidity levels inthe exiting fluid.
 10. The method of claim 1, further comprisingsimultaneously purging a plurality of sorbent tubes with the purginggas.
 11. The method of claim 10, further comprising using a singlehumidity sensor to monitor the humidity levels in each of the pluralityof sorbent tubes.
 12. The method of claim 10, further comprising using aplurality of humidity sensors each fluidically coupled to a singlesorbent tube to monitor the humidity level in each of the plurality ofsorbent tubes.
 13. The method of claim 12, further comprising assigningan address to each of the plurality of humidity sensors to correlate aspecific humidity sensor with a specific one of the plurality of sorbenttubes.
 14. The method of claim 12, further comprising using at least onetemperature sensor fluidically coupled to fluid exiting at least onesorbent tube to determine the humidity level.
 15. A method of purgingwater from a sorbent tube, the method comprising: introducing a purginggas into a sorbent tube; detecting a water level in fluid exiting thesorbent tube with a humidity sensor fluidically coupled to the sorbenttube; and stopping introduction of the purging gas into the sorbent tubeas soon as the detected water level in the exiting fluid is below aselected water level, wherein the purging is stopped when the humiditysensor detects an inflection point from detection of the water level ofthe fluid exiting the purged sorbent tube.
 16. The method of claim 15,in which the selected water level is configured to be about 3% relativehumidity or less.
 17. The method of claim 15, further comprisingactuating a valve between the purging gas source and the sorbent tube toa closed position when the detected water level in the exiting fluid isbelow the selected water level.
 18. The method of claim 15, furthercomprising switching off a gas source providing the purging gas when thedetected water level in the exiting fluid is below the selected waterlevel.
 19. The method of claim 15, further comprising simultaneouslyproviding the purging gas to a plurality of sorbent tubes.